1. Cdc28-Dependent Regulation of the Cdc5/Polo Kinase
Eric M. Mortensen, Wilhelm Haas, Melanie Gygi, Steven P. Gygi, Douglas R. Kellogg 
Current Biology 
Volume 15, Issue 22, Pages (November 2005)
DOI: /j.cub
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2. Figure 1
Cdc28 Is Required for Cdc5 Activity In Vivo and Can Activate Cdc5 In Vitro
(A) cdc28-as1 CDC5-3XHA cells were arrested in mitosis with nocodazole, 25 μM 1NM-PP1 was added, and time points were taken every 5 min. Cdc5-3XHA was immunoprecipitated and kinase activity was assayed by phosphorylation of casein (bottom). Levels of immunoprecipitated Cdc5-3XHA were monitored by Western blotting (top).
(B) A control showing that treatment of wild-type cells with 1NM-PP1 had no effect on Cdc5-3XHA activity. Wild-type Cdc28 cells were arrested in mitosis with nocodazole, 25 μM 1NM-PP1 was added, and a sample was taken 15 min later. Cdc5-3XHA was immunoprecipitated and kinase activity was assayed by phosphorylation of casein.
(C) Cdc28 is required for Cdc5 activity in a normal cell cycle. cdc28-as1 cells were arrested in G1 with α factor and released synchronously into the cell cycle. An initial time point was taken at 75 min as the cells were entering mitosis (lane 1). Identical aliquots of cells were then treated with 25 μM 1NM-PP1 or with DMSO and samples were taken after 7.5 min. Cdc5-3XHA was immunoprecipitated from each sample and kinase activity was assayed by phosphorylation of casein (bottom). The lane marked “Control” corresponds to the sample mock-treated with DMSO.
(D) Activation of Cdc5 by Cdc28/Clb2 in vitro. Wild-type or mutant versions of Cdc5-3XHA were immunoprecipitated from cells arrested in mitosis and incubated in the presence or absence of lambda phosphatase. After washing away the phosphatase, Cdc5-3XHA was incubated in the presence or absence of Cdc28/Clb2 and ATP. Kinase assays were then performed on each sample using casein as a substrate. Cdc5-3XHA protein levels were monitored by Western blotting (top), and kinase activity was assayed by phosphorylation of casein (bottom).
Current Biology  , DOI: ( /j.cub )
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3. Figure 2
Threonine 242 Is Conserved in Members of the Polo-like Kinase Family and Is Required for Cdc5 Kinase Activity In Vitro
(A) Cdc28-consensus site mutants were tested for their ability to support growth in the absence of wild-type Cdc5. Cells dependent upon GAL1-CDC5 were transformed with CEN plasmids carrying the indicated Cdc28 consensus site mutants and tested for growth on media containing galactose or dextrose.
(B) An alignment of activation segment loops in diverse Polo kinases showing that T242 is conserved. Threonine 242 in Cdc5 is indicated by an asterisk.
(C) Wild-type CDC5, cdc5-K110A, and cdc5-T242A were expressed as 3XHA fusion proteins from the GAL1 promoter in cells arrested in mitosis with benomyl. The kinases were immunoprecipitated and assayed for kinase activity by phosphorylation of casein (bottom), and Cdc5-3XHA protein levels in the immunoprecipitates were monitored by Western blotting (top).
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4. Figure 3 Cdc5 Is Phosphorylated on Threonine 242 In Vivo
Cdc5-3XHA was expressed from the endogenous promoter and immunoprecipitated from cells arrested in mitosis. Phosphorylation sites were mapped by mass spectrometry.
(A) A table showing phosphorylation sites mapped by mass spectrometry.
(B) MS/MS spectrum of the doubly charged diphosphopeptide KYTICGTPNYIAPEVLMGK (236–254, m/z) from Cdc5. The threonine residues T238 and T242 were identified to be phosphorylated as indicated by asterisks. Predicted m/z values for the b- and y-type ions are listed and ions observed in the MS/MS spectrum are in bold font.
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